FR2774692A1 - BENTONITE-BASED DRILLING MUD AND DRILLING METHOD USING THE SAME - Google Patents

Abstract

Disclosed is a bentonite-based drilling mud, which comprises a phosphonate compound of the formula: (CF DRAWING IN BOPI) wherein R1, R2, R3 and A are as defined in the description. The invention also relates to a drilling method which uses said mud.

Description

The present invention relates to the field of drilling muds.

  The majority of bentonites for drilling mud available on the market are calcium bentonites made artificially sodium by exchange of calcium ions naturally present in the structure, by sodium ions, in general by a treatment with carbonate of

sodium in the factory.

  Drilling muds prepared with sodium bentonite have rheological properties far superior to those of muds

  prepared with calcium bentonite.

  However, the rheological characteristics of the sludge deteriorate on contact with calcium either from the lime of the cement, during concreting for example, or from the calcium available in the

land like gypsum for example.

  To remedy the deterioration of the rheological characteristics of drilling mud during the works, it is usually treated with sodium bicarbonate when there is pollution by the lime of the cement or with sodium carbonate when there is pollution by gypsum. Free and mobile calcium ions are thus removed from the drilling mud by precipitation of

calcium carbonate.

  This treatment has the disadvantage of being temporary, since the calcium stored in the cement or in the gypsum goes into solution as and when

  measurement of the precipitation of calcium carbonate.

  To maintain suitable rheological characteristics, constant monitoring of the mud and permanent addition of bicarbonate or sodium carbonate are necessary during the works. In addition, the treatment of the mud with sodium carbonate or bicarbonate is sometimes followed by thickening and stiffening.

  unwanted mud due to carbonate ion pollution.

  Complementary treatment with sodium polyacrylate, which is

  a dispersing-fluidizing agent is then necessary.

  The Applicant has found, unexpectedly, that the incorporation of phosphonate-type compounds in bentonites for drilling mud makes it possible to resolve these drawbacks. In particular, this incorporation allows: - blocking of free calcium ions in the form of soluble and stable complexes; - the conservation or the restitution of the initial fluidity of the mud

  phosphonates also have a dispersing effect on mud-

  thinner. Thus, according to a first aspect, the invention relates to a bentonite-based drilling mud, which comprises a compound of phosphonate type. Bentonites for drilling mud which it is possible to use 0o within the framework of the invention include all bentonites

  commonly used in this field.

  The phosphonate type compounds to be incorporated in the drilling muds of the invention correspond to the general formula R2OA 12 1

R1 C- P = -O

  I I R3 OA in which: - R1, R2 and R3, independently of each other, represent hydrogen; hydroxy; a (C1-C8) alkyl optionally substituted by a group -NR4R5 or by a phenyl; phenyl; or a phosphono group; - R2 and R3 can also form, with the carbon atom to which they are linked, a phenyl; - R4 and R5, independently of one another, represent hydrogen; or a (C1C8) alkyl optionally substituted by an amino; each A independently represents hydrogen; an atom of

sodium; or a potassium atom.

  By way of example of compounds of phosphonate type advantageous for the implementation of the invention, there may be mentioned in particular the sodium or potassium salts of the following acids: - hydroxyethylidene-1,1-diphosphonic acid - aminotrimethylenephosphonic acid - acid ethylenediaminetetramethylenephosphonic acid - diethylenetriaminepentamethylenephosphonic acid - hexamethylenediaminetetramethylenephosphonic acid - octylphenylphosphonic acid Preferably, 0.2 to 10 parts by weight of compound are used

  phosphonate type per 100 parts by weight of bentonite.

  The drilling muds according to the invention can also contain additives commonly used in this field, such as for example sodium (bi) carbonate, in a proportion of 2 to 10 parts by weight of additive.

  per 100 parts by weight of bentonite.

  The drilling mud according to the invention can be prepared by mixing the bentonite and the phosphonate compound in the presence of water. According to a particular embodiment of the invention, the powdered bentonite is premixed with the powdered phosphonate type compound. The drilling mud is then prepared using the mixture

powder and water.

  The invention also relates to a drilling method in which

  drilling mud is used as defined above.

  The drilling muds according to the invention have essential advantages compared to conventional muds: - they allow a durable treatment, - they are as effective in preventive treatment as curative, - they allow to replace two products by only one,

  - they have a considerably extended lifespan.

  The invention will be better understood using the examples below,

  given for illustrative purposes only.

EXAMPLES

  Example 1: Use of phosphonates in preventive treatment The drilling mud is prepared having the following composition: Water 1000 liters sodium bentonite 45 kg Phosphonate * 3 liters (i.e. 2.3 kg per 100 kg of bentonite) * Hexamethylenediaminetetramethylenephosphonic acid solution,

  28% potassium salt (density 1.24).

  The sludge thus treated preventively retains its characteristics

rheological in contact with cement.

  Example 2: Use of phosphonates in curative treatment

  Or a drilling mud dosed at 50 kg of bentonite per m3 of water.

  After the perforation of the secondary panels of a diaphragm wall, the dissolved calcium in the concrete of the primary panels led to a degradation of the rheological properties of the mud. Good to know: Filtrate 82 ml Cake 7 mm Viscosity MARSH> 120 s io After treatment of the mud with a solution of diethylenetriaminepentamethylenephosphonic acid, sodium salt (density 1.33), at the rate of 2 liters per m3 (i.e. 1 kg of phosphonate per 100 kg of bentonite), the characteristics have returned to normal: Filtrate 22 ml Cake 0.5 mm Viscosity MARSH 36 s Example 3: Preventive treatment of bentonite in powder form 6 parts by weight of diethylenetriaminepentamethylenephosphonic acid, salt sodium with 100

  parts by weight of bentonite powder.

  The mixture thus produced is used to make a slurry of

  drilling dosed at 40 kg of mixture per m3 of water.

  The characteristics of the mud do not undergo any modification after the addition of 5 kg / m3 of Portland cement while the same mud does not

  treated has all of its degraded characteristics.

Claims (6)

  1. Bentonite-based drilling mud, which comprises a compound of phosphonate type.   2. A drilling mud according to claim 1, in which the phosphonate type compound has the following formula R OA 12 1 R1 C-P = O   I I R3 OA in which: - R1, R2 and R3, independently of each other, represent hydrogen; hydroxy; a (CI-C8) alkyl optionally substituted by a group -NR4Rs or by a phenyl; phenyl; or a phosphono group; - R2 and R3 can also form, with the carbon atom to which they are linked, a phenyl; - R4 and R5, independently of one another, represent hydrogen; or a (C1C8) alkyl optionally substituted by an amino; each A independently represents hydrogen; an atom of sodium; or a potassium atom.   3. drilling mud according to claim 1 or 2, in which the phosphanate type compound is chosen from the sodium or potassium salts of the following acids: - hydroxyethylidene-1,1-diphosphonic acid - aminotrimethylenephosphonic acid 2s - ethylenediaminetetramethylenephosphonic acid - diethylenetriaminepentamethylenephosphonic acid - hexamethylenediaminetetramethylenephosphonic acid - octylphenylphosphonic acid.   4. Drilling mud according to one of claims 1 to 3, in which   the phosphanate compound is present in an amount of 0.2 to 10 parts   by weight per 100 part by weight of bentonite.   5. drilling mud according to one of claims 1 to 4, which is obtained from a premix of bentonite and of the type compound   phosphonate. 6. Drilling method, in which the mud of   drilling according to one of claims 1 to 5.